In the development of an electric current measuring apparatus utilizing the Faraday effect, it is necessary to measure the intensity of two different light beams. Also, it is necessary, for each of the light beams, to compute the ratio of the alternating, AC, component of the intensity to the constant, DC, component of the intensity.
It is further necessary to compute a quotient by dividing an average value of the above ratio for the first light beam by an average value of the ratio for the second light beam.
Further, in those situations in which it is desired to make a measurement of electric current flow by use of the Faraday effect, and to make the measurement to a precision of 0.1%, it is necessary to compute the quotient to an accuracy of better than 0.1%.
Existing light detectors have been found inadequate to compute the above mentioned quotient, and further, to compute such a quotient to an accuracy of better than 0.1%.